Reduction of leachability and solubility of radionuclides and radioactive substances in contaminated soils and materials

ABSTRACT

A process for chemical fixation of radionuclides and radioactive compounds present in soils, solid materials, sludges and liquids. Radionuclides and other radioactive compounds are converted to low-temperature Apatite-Group structural isomorphs (general composition: (AB) 5 (XO 4 ) 3 Z), usually phosphatic, that are insoluble, non-leachable, non-zeolitic, and pH stable by contacting with a sulfate, hydroxide, chloride, fluoride and/or silicate source and with a phosphate anion in either a one or two step process. The Apatitic-structure end product is chemically altered from the initial material and reduced in volume and mass. The end product can be void of free liquids and exhibits sufficiently high levels of thermal stability to be effective in the presence of heat generating nuclear reactions. The process occurs at ambient temperature and pressure.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application under 37 C.F.R. §1.53(b)of U.S. application Ser. No. 08/953,568, filed Oct. 17, 1997 now U.S.Pat. No. 5,994,608, which is a continuation of application Ser. No.08/663,692, filed Jun. 14, 1996 now U.S. Pat. No. 5,732,367, which is aContinuation-in-Part of application Ser. No. 08/031,461, filed on Mar.15, 1993, now U.S. Pat. No. 5,527,982; which is a Continuation-in-Partof application Ser. No. 07/721,935, filed Jul. 23, 1991, now U.S. Pat.No. 5,193,936 (Reexamination Certificate issued on Mar. 19, 1996); whichis a Continuation-in-Part of application Ser. No. 07/494,774, filed Mar.16, 1990, now abandoned. All of these prior applications are herebyincorporated herein by reference.

FIELD OF THE INVENTION

The present invention pertains to the field of chemical fixation ofhazardous waste materials, including metal-bearing materials andradionuclides and radioactive substances, in debris, soils, solidmaterials, sludges and materials precipitated or filtered from liquids,rendering such hazardous waste materials within a stabilized, insoluble,non-leachable, non-zeolitic and pH stable form suitable for safe andecologically-acceptable disposal; typically regulated by the U.S.Department of Energy, the U.S. Environmental Protection Agency(“USEPA”), and others. The ecologically safe state of the treatedmaterials is not altered by exposure of the treated materials to acidicleachate, acid rain, or radioactive groundwater. In addition, the safestate of the treated materials is not altered by exposure to changingweather conditions; including rain, heat, freeze and thaw.

BACKGROUND OF THE INVENTION

Various forms of hazardous wastes pose a serious threat to theenvironment and safe and cost efficient methods for treating anddisposing of these wastes has become increasingly important.

Hazardous wastes containing excessive amounts of leachable lead arebanned from land disposal. The regulatory threshold limit under ResourceConservation and Recovery Act is 5 mg/l of leachable lead as measured byTCLP (toxicity characteristic leaching procedure) test criteria, UnitedStates Environmental Protection Agency (USEPA) method 1311 (SW-846).Waste materials containing TCLP lead levels in excess of 5 mg/l aredefined as lead-toxic hazardous waste and are as such restricted fromland-filling under current land ban regulations. The cost of disposinglead toxic hazardous waste materials is in excess of $200.00 per tonplus the cost of transporting the hazardous material to landfills forhazardous wastes, which do not exist in every state. This makes thedisposal of lead toxic hazardous waste material very expensive.Therefore, treating the lead-bearing process materials and waste streamsto render them non-hazardous by RCRA definition would cut down the costsof transportation and disposal tremendously.

Conventional treatment methods for radionuclides and other radioactivesubstances can be categorized into three groups: 1) separation; 2)structural containment; and 3) physical stabilization/solidification.These treatment methods are complex, costly, expand volumes, and areonly temporary solutions.

Various conventional methods have been tried to remove leachable, mobileradionuclides and radioactive substances from soils and other materials.Removal of contamination from soils and solid materials by leaching,centrifugation, extraction and/or washing procedures is extremelyexpensive and cost-prohibitive because these methods generate vastquantities of contaminated liquid wastes which require further treatmentand disposal.

Conventional solidification methods based on cementation technologyrequire up to twenty-eight (28) days curing time, increase the wastevolume and may raise the pH above 12.5. USEPA defines a pH above 12.5 ashazardous. Hardened cementitious material is not conducive toretreatment in the event treatment fails obligatory confirmationtesting. Solidification methods utilizing lime kiln dust, calciumcarbonate and/or powdered lime for fixation are, at best, temporarysolutions. Furthermore, these methods increase the waste volume andmass. A primary concern is that cementitious methods dilute theparameters of concern in the final waste matrix.

In the past, radionuclide and radioactive wastes have been temporarilystored; frequently as a liquid, a sludge, or a contaminated fine-grainedsolid in conjunction with contaminated soils. The art has recognizedthat a means must be provided for permanent disposal of these wastes,preferably as non-leachable solids, containing non-migratoryradionuclides. Such solids must have certain characteristics which makethe solids safe and economical for the long term (10³ to 10⁶ years)retention of radioactive isotopes.

SUMMARY OF THE INVENTION

The present invention discloses a method of treating hazardous wastematerials, including metal-bearing materials and radionuclides andradioactive substances.

One embodiment of the present invention relates to a chemical treatmenttechnology for immobilizing leachable lead in contaminated soils andsolid waste materials. According to the present invention, a process fortreating lead-toxic solid wastes in order to stabilize the leachablelead is disclosed, comprising the steps of: (i) mixing the solid wastewith a sulfate compound, such as calcium sulfate dihydrate (gypsumpowder) or sulfuric acid, having at least one sulfate ion for contactingwaste particles and reacting with said leachable lead to produce asubstantially insoluble lead composition, such as anglesite and/orcalcium-substituted anglesite; and, (ii) mixing said solid waste andsulfate compound with a phosphate reagent, such as phosphoric acid,having at least one phosphate ion for reacting with said leachable leadto produce a substantially insoluble lead composition. The treatedmaterial from this process is substantially solid in form and passes thePaint Filter Test while satisfying the regulatory standard for TCLPlead. In all instances, application of this process has been found veryreliable in meeting the treatment objectives and in consistentlydecreasing waste volume.

It is an object of the present invention to provide a technology fortreatment of lead-containing solid waste and soil that produces anacceptably low level of leachable lead in the final product to complywith the statutory requirements of TCLP and to pass the Paint FilterTest.

Another object of the invention is to provide such a process whileproducing no wastewater or secondary waste streams during said process.

Still another object of the invention is to provide such a process whichalso causes the solid waste material to undergo a volume reduction as aresult of treatment.

Yet another object of the invention is to cause fixation of theleachable lead in the solid waste that is permanent under both ordinaryand extreme environmental conditions.

The present invention relates to treatment methods employed tochemically convert leachable metal in metal-bearing solid and liquidwaste materials to a non-leachable form by mixing the material with oneor a combination of components, for example, lime or gypsum andphosphoric acid. The solid and liquid waste materials includecontaminated sludges, slurries, soils, waste waters, spent carbon, sand,wire chips, plastic fluff, cracked battery casings, bird and buck shotsand tetraethyl lead contaminated organic peat and muck. Themetal-bearing materials referred to herein which the present inventiontreats include those materials having leachable lead, aluminum, arsenic(III), barium, bismuth, cadmium, chromium (III), cooper, iron, nickel,selenium, silver and zinc. The present invention discloses a processcomprising a single step mixing of one or more treatment additives, anda process comprising a two step mixing wherein the sequence ofperforming the steps may be reversible. The present invention provides anovel way of treating a plurality of metal-contaminated materials at awide range of pH. The method works under acidic, alkaline and neutralconditions.

The processes of the present invention provide reactions that convertleachable metals, especially lead, into a non-leachable form which isgeochemically stable for indefinite periods and is expected to withstandacid rain impacts as well as the conditions of a landfill environment.

A first group of treatment chemicals for use in the processes of thepresent invention includes lime, gypsum, alum, halites, Portland cement,and other similar products that can supply sulfates, halites, hydroxidesand/or silicates.

A second group consists of treatment chemicals which can supplyphosphate ions. This group includes products such as phosphoric acid,pyrophosphates, triple super phosphate (TSP), trisodium phosphate,potassium phosphates, ammonium phosphates and/or others capable ofsupplying phosphate anion when mixed with a metal-bearing processmaterial or with a metal-toxic hazardous waste. Depending on the processmaterial or waste (i) matrix (solid, liquid or mixture thereof), (ii)category (RCRA or Superfund/CERCLIS), (iii) chemical composition (TCLPlead, total lead level, pH) and (iv) size and form (wire fluff, shots,sand, peat, sludge, slurry, clay, gravel, soil, broken battery casings,carbon with lead dross, etc.) the metal-bearing material is mixed withone or more treatment chemicals in sufficient quantity so as to renderthe metal substantially non-leachable, that is, to levels below theregulatory threshold limit under the TCLP test criteria of the USEPA.For lead-bearing materials, the treatment additives render the leadbelow the regulatory threshold limit of 5 mg/l by the TCLP test criteriaof the USEPA. The disposal of lead-hazardous and other metal-hazardouswaste materials in landfills is precluded under land ban regulations.

It is an object of the present invention to provide a method of treatingmetal-bearing materials, contaminated soils and waste effluent, andsolid wastes containing hazardous levels of leachable metal. It is afurther object to provide a method which decreases the leaching of leadin lead-bearing materials to levels below the regulatory limit of 5 mg/lby TCLP test criteria.

It is another object of the present invention to provide a method toimmobilize lead to leachable levels below 5 mg/l by TCLP test criteria,through the use of inexpensive, readily accessible treatment chemicals.With this method, the leachability of lead is diminished, usuallyallowing municipal landfill disposal which would not otherwise bepermitted.

Yet another object of the present invention is to provide a treatmentmethod for metal-bearing wastes, particularly lead-bearing wastes, whichcomprises a single step mixing process or a two-step process wherein thesequence of the two steps may be reversed.

Another object of the present invention is to provide a method oftreating a wide variety of lead bearing process materials, wire fluffand chips, cracked battery plastics, carbon with lead dross, foundrysand, lead base paint, leaded gasoline contaminated soils, peat andmuck, sludges and slurries, lagoon sediment, and bird and buck shots, inorder to render the material non-hazardous by RCRA definition, and passthe EPTOX, MEP, ANS Calvet and DI Water Extract tests.

Another object of the present invention is to extend the scope for broadapplication in-situ as well as ex-situ on small as well as largequantities of metal-bearing process materials or generated wastestreams.

The present invention provides a method which converts metal-toxicprocess materials and hazardous wastes into a material which has a lowerleachability of metal as determined by EPA's TCLP test. Such treatedwaste material can then be interned in a licensed landfill, a method ofdisposal only possible when the leachability of metal isdiminished/reduced to levels below the regulatory threshold limit byTCLP test criteria, e.g., lead below 5 mg/l.

Another embodiment of the present invention relates to a chemicaltreatment process that reduces the leachability and solubility ofradionuclides and other radioactive substances contained in debris,soils, sludges and solid materials (“the host material” or “the hostmatrix”). The process for treating radionuclides and other radioactivesubstances employs the same methods and treatment chemicals used fortreating metal-bearing hazardous waste materials. The process comprisescontacting radionuclides and other radioactive substances in the hostmatrix with the first and second group treatment chemicals to promoterecrystallization of the host material into Apatitic-structuredend-products. Preferred reactants are comprised of at least onephosphate group and create mineral species of Apatitic geometricstructures with reduced nuclide leachability and solubility. In thepreferred embodiment, technical grade phosphoric acid (TGPA) is used ina one step process. TGPA contains sulfate as an impurity in addition toa phosphate anion source.

The Apatite-structure ((AB)₅(PO₄)₃Z) is preferred since the anion Zposition is usually a halogen or a hydroxyl, both active scavengers ofcations. The unique properties of the Apatitic-structure, (AB)₅(XO₄)₃Z,are key to this invention. Just as low-temperature Apatite is nature'sion-prison in the biological/biosphere environment and high-temperatureApatite is natures ion-prison in the pegmatites/igneous lithosphereenvironment, Apatites can do the same in man-made (unnatural/synthetic)radioactive environments. The supplementary problem of metamict latticedisruptions, from the generation of excess heat and ion-cannon recoildamage by radioactive decay, is also self-resolved in Apatites.

Both low-temperature and high-temperature Apatitic-structures areself-healing and non-leaching. In one embodiment of the presentinvention, the flow of normal groundwater through the treated materialshould be encouraged since the groundwater will disperse the build-up ofheat and eliminate the requirement for costly cooling of monolithicencasement structures. In another embodiment of the present invention,treated material contacted with groundwater contaminated withradionuclides and radioactive substances reduces the radioactive levelof the ground water.

Natural scavenging of Lanthanides and Actinides by Apatitic-structurephosphate-complexing phases is well-documented from research conductedin connection with the mining of oceanic deposits throughout the worldto produce phosphate products. To date, more than 300 Apatite mineralspecies have been classified by geologists.

Substitution within Apatites are extremely complex. Many require acharge-compensating mechanism that can be grossly estimated from ionicradii and coordination numbers. Common substitution mechanisms noted areas follows: 1) simple within-site substitutions; 2) coupledsubstitutions involving chemically similar cations; 3) substitutionsinvolving large cations, such as Cs, with smaller cations; 4)substitutions involving cation vacancies; 5) substitutions couplingspecific cations with specific anions; 6) substitutions involvinganions; 7) substitutions involving anion vacancies; and 8) substitutionsinvolving a change in valence.

From the structural and compositional studies of natural and syntheticApatites, it is known that Apatites are complex geological structures.The present invention has found that Apatites can sustain a greatvariety of substitutions following the general formula (AB)₅(XO₄)₃Z,[sometimes written, (AB)₁₀(XO₄)₆Z₂], wherein:

A = Coordination Number 7 thru 12, most commonly 9. Cations smaller thanMn⁺² are to small for an 8 coordination number, unless combined with alarger cation. = Ca, Sr, Mn, Pb, Mg, Ba, Zn, Cd, Fe, Ni, Co, Sn, Eu, Cu,and Be among divalent elements. = Na, K, Rb, Ag, Cs and possibly Liamong monovalent elements. = Al, Fe, Y, rare earth elements (REE) exceptEu and Ce, Bi and possibly Nb, Sb and Ti among trivalent elements. = U,Pb, Th, Zr, Ce, Transuranics and possibly Tl among quadrivalentelements. = [] minor lattice vacancies. B = Coordination Number 6 thru9, most commonly 8. Cations smaller then W⁺⁶ are small for 6coordination number and those larger than Zr⁺⁴ are too large. = Ca, Sr,Mn, Pb, Mg, Ba, Zn, Cd, Fe, Ni, Co, Sn, Cu, and Be among divalentelements. = Na, K, Rb, Ag, Li possibly among monovalent elements. = Al,Fe, Sc, Sb, Y, Eu and Ce REE, Nb, Bi and possibly Ta among trivalentelements. = Si, Mn, Ti, Mo, W, Sn, U, Th, Zr, C among quadrivalentelements. = Actinide ion species conforming to Metal.O₂ (especiallyUO₂). = [] minor lattice vacancies. XO₄ = PO₄, SiO₄, SO₄, AsO₄, VO₄,CrO₄, BeO₄, MoO₄, CO₃, CO₃F, WO₄, MnO₄, CO₃OH, BO₄, AlO₄, Fe₃O₄,possibly GeO₄, and SeO₄. Z = F, OH, Cl, Br, I, O and [] minor latticevacancy in structure of defective Apatites.

Element 43—Technetium is effected by the process with leachabilitygreatly reduced; however, its positioning within the Apatitic-structurehas not been determined with certainty.

Additionally, the radius ratios among A, B and XO₄ components, and theirrespective coordination number, can have a strong influence on theApatite-structure. Problems occur when an element's ionic radius issmall for A and large for B; therefore, a single site cannot beconsidered alone and a partitioning between A and B sites is proposed.The partitioning is extremely difficult to predict since the amountsinvolved may be very minor as well as promoting localized crystaldisorder.

In its simplest and most efficient form, the current invention providesfor the addition of at least one member selected from a first group oftreatment chemicals that can supply sulfates, halides, hydroxides and/orsilicates and at least one member selected from a second group oftreatment chemicals that can supply phosphate ions to materialconsisting of, or containing, radionuclides and other radioactivesubstances. Technical grade phosphoric acid (“TGPA”) that contains up to70% (by weight) phosphate (as P₂O₅) and sulfate (SO₄ ⁻²), typically assulfuric acid in the range of 2.5% to 7% (by weight) as an impurity, isa source of both a sulfate ion and a phosphate ion and can, therefore,be used as a single reactant. The addition of water at any point in theprocess aids in the dispersion of the TGPA throughout the host matrix.As the TGPA disperses and permeates through the matrix and during thecourse of subsequent reactions, the leachability and solubility ofradionuclides and other radioactive substances is reduced. Supplementalmechanical or physical mixing can also be employed to enhance thecontact of the TGPA with the leachable species in the host material.

As a true chemical process, an object of the invention relies onmolecular bonding and crystal nucleation principles to reduce nuclidesolubility and to create conditions suitable for matrix volume reductionresulting, in part, from the dehydration properties of the treatmentchemicals. When TGPA is utilized, molecular rearrangement and minimizedaddition of treatment agents is characteristic of the invention andsupplemental buffering agents or traditional strength enhancementphysical-binding additives typical of physically stabilized mixtures arenot required. The end-product of the invention is a material thatcontains no free liquids and produces no supernatant wastewater orsecondary waste streams. A further loss of water weight is achieved bycapillary drying and evaporation which also contribute to volumereduction. Some volume reduction can be attributed to acidic carbonatedestruction, especially those not incorporated into the Apatiticstructures. The end product is friable and can be handled withtraditional earth-moving equipment, as it is not monolithic in form.

Moreover, the end-product can be made to have enhanced geotechnicalproperties without compromising the chemistry of the nuclideleachability/solubility reduction. The addition of water, either tosuppress dust or due to rainfall, and excavation or other materialhandling activities do not affect the nuclide leachability or solubilityof the end-product.

Another object of the invention is to increase the level of protectionoffered by disposal facility designs engineered specifically to control,isolate, or contain material characterized with leachable radionuclides;and to minimize the migration of radionuclides and other radioactivesubstances from material that is accessed by the percolation of rain andsurface waters, and/or the intrusion and flow-through of groundwater orleachate that can act as an ion-carrier. When groundwater contaminatedwith radionuclides and radioactive substances are contacted withmaterials treated by the present invention, the radioactive level of thegroundwater will be reduced. The radionuclides and radioactivesubstances in the groundwater react with the phosphate compounds andsulfate compounds in the treated materials to form geochemically stableApatite-structures.

A further object of the present invention is the addition of liquid orsolid reagents to a solid material or sludge without creating secondarybyproducts or separable streams. Another object of the present inventionis to engage and employ preexisting carbonates, borates, sulfates,and/or silicates within the matrix at the time of phosphate anionaddition so that they contribute to the formation of Apatitic-structuresthat reduce nuclide leachability and solubility and host matrix volume.An additional objective of the invention is the immediate initiation ofprocess reactions upon the contacting of phosphate anion with theleachable or soluble species, without the separation of nuclides orother byproducts from the matrix. Another objective is the in situ or exsitu application of process reagents to nuclide material; whereinfixation of the nuclides is permanent under both ordinary and extremeenvironmental conditions. Still another object of the invention is theuse of acidity to enhance dissassociation of semi-soluble species sothat problematic nuclides are freed to nucleate within the Apatitecrystals. These and other objects will be apparent from the detaileddescription of the invention set forth below.

The invention may be more fully understood with reference to theaccompanying drawings and the following description of the embodimentsshown in those drawings. The invention is not limited to the exemplaryembodiments but should be recognized as contemplating all modificationswithin the skill of an ordinary artisan.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 exhibits the single step mixing method of treatment chemicalsmetered into the pugmill or Maxon Mixer capable of processing leadhazardous waste materials at rates up to 100 tons/hour;

FIG. 2(a) exhibits the two step mixing with addition of group onetreatment chemicals during step I and addition of group two treatmentchemicals during step II;

FIG. 2(b) exhibits the two step mixing method with addition of group twotreatment chemicals during step I and addition of group one treatmentchemicals during step II. The reversibility of steps and combination ofboth steps into a single step is the discovery that is disclosed in thisinvention and illustrated in FIGS. 1 and 2(a) and (b).

FIG. 3 exhibits an embodiment of the invention which mixes gypsum and aliquid reagent to treat contaminated soil or toxic waste.

DESCRIPTION OF THE PREFERRED EMBODIMENT

According to the present invention, leachable lead in treated materialsis decreased to levels well below 5.0 mg/l, measured by TCLP testcriteria. Waste and process materials having TCLP lead level in excessof 5 mg/l are considered hazardous and must be treated to be broughtinto compliance with regulatory requirements. Other metal-bearingmaterials having leachable metals may also be treated according to thepresent invention to achieve acceptable metal levels.

The treatment technology according to another embodiment of the presentinvention consists of a two step process for treating contaminated soilsand/or solid waste materials with chemical treating agents that convertleachable lead to synthetic (man-made) substantially insoluble leadmineral crystals. As used here, “substantially insoluble” means theleachable lead content in the treated waste sample is less than 5.0 mg/lin the extract by the TCLP Test.

Another preferred embodiment of the present invention consists ofapplying technical grade phosphoric acid (TGPA) that contains sulfate asan impurity to leachable and soluble radionuclides and other radioactivesubstances often found in debris, soils and solid materials. Theaddition of water aids in the dispersion and percolation of TGPAthroughout the contaminated host matrix. Water can be added at any pointof the process, either before or after the TGPA addition, or by dilutingthe TGPA and applying the dilute TGPA to the target matrix. Mixing ofthe TGPA with the host matrix is optional, dependent upon thepermeability and porosity of the host material. When employed, mixingenhances the uniformity of reagent dispersion through the host material.

Treatment Chemicals and Additives

The treatment chemicals useful in the present invention may be dividedinto two groups. The addition of water with the additives may facilitatethe ultimate mixing and reaction.

A first group, “group one”, comprises a source of sulfate, hydroxide,chloride, fluoride and/or silicates. These sources are gypsum, lime,sodium silicate, cement, calcium fluoride, alum and/or like similarproducts.

The second group, “group two”, comprises a source of phosphate anion.This group consists of products like phosphoric acid (phosphoric),pyrophosphates, triple super phosphate, trisodium phosphates, potassiumphosphates, ammonium phosphates and/or similar compounds capable ofsupplying a phosphate anion.

The first step of this novel process comprises the reaction of leachablelead in contaminated soils or solid waste materials with a gypsumpowder, calcium sulfate dihydrate (CaSO₄.2H₂O). Calcium sulfatedihydrate powder reacts with leachable and mobile lead species in wastesto form hard sulfates, which are relatively insoluble in water. In theinvention, the powder form of dry calcium sulfate dihydrate, or gypsum,is preferred for blending with lead contaminated materials because itprovides a uniform cover or dry coating over the surfaces of the wasteparticles and aggregates under low moisture conditions. The greatestbenefit and fastest reaction is achieved under conditions wherein 95% ofthe powder is passable through a 100 mesh sieve, and the remaining 5% ispassable through a 20 mesh sieve.

The amount of gypsum powder employed is typically from 0-30 percent ofthe weight of solid waste material being treated. The actual amountemployed will vary with the degree and type of lead contamination in thewaste material or soil, and with the initial composition as well as thecondition of the waste material, among other factors.

Alternatively, sulfuric acid, or alum in liquid or powder form can alsobe used as sources of sulfate ion in certain solid wastes that containsufficient calcium prior to treatment.

Treatment Method

At lease one component from group one is added to the mixing vessel orreactor, preferably as a dry powder, although slurries could be pumpedunder certain circumstances. At least one component from group two isadded to the mixing vessel or reactor as either liquid reagent or asgranular solid materials.

The ingredients of group one and group two can be added to the hazardouswaste materials simultaneously, and they are pre-mixed and added in asingle step. Alternatively, the components of group one and two can beadded sequentially in a two-step process with either component addedfirst. That is, the two steps may occur in any order. At least oneingredient of group one can be added in step I or step II. Likewise, atleast one ingredient of group two can be added in either step I or stepII. Enough water may be added to allow good mixing to prevent dustformation, and to permit good chemical reaction. Not too much water isadded to solid materials if the treated waste is to pass the paintfilter test.

In the first step of the instant process, a thorough and uniform mixingof gypsum powder with the solid waste is accomplished by mixing shreddedand screened waste particles with small gypsum particles in, forexample, a grizzly or other mixing device. The calcium ions from thegypsum powder displace lead from soil complexes and organic micellespresent in the contaminated soil and solid waste material The followingequations (1) and (2) describe the reaction of leachable lead withgypsum.

The reaction of lead with gypsum forms a “hard sulfate” whichcrystallizes into mineral species of the barite family—anglesites andcalcium-substituted anglesites—which are insoluble in water. Thesolubility product of lead sulfate is 1.8×10⁻⁸, indicating thatanglesite crystals would continue to develop over the geologic periods.

In the second step of the process, the solid waste material as amendedwith gypsum powder is treated with a phosphate-supplying reagent, suchas (for example), phosphoric acid. Upon contact with the soil or solidwaste, the phosphate-supplying reagent reacts chemically to immmobilizethe remaining leachable lead. The phosphate-supplying reagent includesphosphate ion sources having one or more reactive phosphate ions, suchas phosphoric acid, trisodium phosphate, a potassium phosphate andmonobasic or dibasic calcium phosphates.

The quantity of phosphate-supplying reagent employed will vary with thecharacteristics of the solid waste being treated, including particularlysuch factors as leachable lead content, total lead, and bufferingcapacity, among other factors. It has been determined that in mostinstances a quantity of phosphoric acid up to 30 percent of the weightof the waste material is sufficient. The concentration of phosphoricacid in solution will typically range from about 2 to 75 percent byweight. The solution and treatment process are maintained above 30° F.to permit the handling of the phosphoric acid as a liquid reagent. Below30° F., the phosphoric acid tends to gel while water freezes to formice, thus creating material handling problems.

Free lead, along with calcium ions found in the solid waste (includingthose imparted through the first step of the process), reacts with thephosphate to form insoluble superhard rock phosphates or calciumsubstituted hydroxy lead Apatites as shown in Equations (3a) and (3b):

The phosphate ions are added to the contaminated soils in solution form;for example, phosphoric acid may be added to water in amounts rangingfrom about 2 percent to about 75 percent by weight. Phosphoric aciddecomposes carbonates and bicarbonates in wastes leading to thesynthesis of Apatites and evolution of carbon dioxide gas. Destructionof carbonates and bicarbonates contributes to desirable volumereductions.

Although water molecules are generated during the carbonate andbicarbonate decomposition process, it is preferred to have soil moistureat about 10 per cent to about 40 per cent by weight of the soil in orderto accelerate the fixation of the leachable lead with the phosphateions. At this moisture range, material handling is also easy andefficient. It is apparent from Equations (2), (3a) and (3b) that gypsumand phosphoric acid decompose carbonates and bicarbonates duringsynthesis of new stable minerals of the barite, apatite, andpyromorphite families in soils (as shown in Table I). Decomposition ofcarbonates and bicarbonates is usually associated with the evolution ofcarbon dioxide, formation of hydroxyl group, (OH—), and the release ofwater molecules. As the water evaporates and carbon dioxide moleculesare lost to the atmosphere, the treated waste mass and volume aredecreased significantly.

The solid sulfate powder and the phosphate-supplying reagent are addedto contaminated soil and solid waste material having a typical moisturecontent ranging from about 10 percent to about 40 percent by weight. Ata moisture level within the foregoing range, the curing time of thetreated materials is approximately 4 hours, which provides adequate timefor chemical reactions to occur and immobilize the leachable leadspecies. Crystals of various lead mineral species begin to formimmediately, but will continue over long time periods with an excess oftreatment chemicals present. This contributes to “self-healing,” asnoted during treatability studies as well as full scale treatmentoperations.

Under the foregoing conditions, the immobilization of leachable leadoccurs in a relatively dry environment because no wet byproducts,slurries or wastewater are produced by the process of the presentinvention. Operation of the process under relatively dry conditionsbeneficially allows cost-efficient handling of the contaminated soilsand the waste materials. This allows compliance with Paint Filter Testfor solid wastes required by USEPA and RCRA approved solid wastelandfill facilities. Effective mechanical mixing, as by a pug mill orother such mixing device, eliminates the need for diffusion in thenonaqueous solid waste matrix.

The water resistant and insoluble lead minerals synthesized in soils andsolid wastes according to this process are stable, and would behave likenaturally occurring rock phosphates and hard sulfates. A list of thesesynthetic lead mineral species and complexes is presented in Table Ibelow, in order of the relative abundance found during characterizationof treated soil by x-ray florescence spectrometry, polarized lightmicroscopy (PLM) and scanning electron microscopy (SEM).

TABLE I SYNTHETIC MINERAL SPECIES OF LEAD DETECTED IN A TREATED SAMPLE(LISTED IN DECREASING ORDER OF ABUNDANCE) 31-41% Calcium SubstitutedHydroxy Lead Apatites, Ca_(0.5-1.5)Pb_(3.5-4.5)(OH)(PO₄)₃ 28-29% MixedCalcium Lead PHosphate Sulfates,Ca_(0.05-0.2)Pb_(0.8-0.95)(PO₄)_(0.15-0.5)(SO₄)_(0.25-0.75) 20-22% MixedCalcium Anglesites, Ca_(0.05-0.3)Pb_(0.7-0.95)(SO₄)  3-6% Anglesites,PbSO₄  2-7% Lead Hydroxy/Chlor Apatite, Pb₅(PO₄)₃(OH)_(0.5)Cl_(0.5) 1-3% Pyromorphite, Pb₃(PO₄)₂  1-2% Organo-Lead Phosphate Sulfate,Humus-o-Pb₃(PO₄)(SO₄)

Some of the chemical reactions that occur during the curing stage, andlead to the development of mixed minerals containing both sulfates andphosphates, are illustrated in Equations (4) and (5).

The process of the present invention beneficially decreases the volumeof the waste materials through: (i) the evolution of carbon dioxideduring the chemical decomposition of carbonates and bicarbonates, uponreaction with the acidic components in gypsum and phosphoric acid, and(ii) hardening and chemical compaction as a result of the synthesis ofnew minerals which result in changes in interstitial spaces andinterlattice structures. Applications of the process on a leadcontaminated soil was associated with pore space decrease from 38.8% to34.3% by volume. A decrease in pore space was associated with increasedcompaction of the treated soils and a decrease in overall waste volumeranging from 21.4% to 23.0%. For different waste types, the volumedecrease varies with the amount of treatment chemicals used in theprocess. In another lead toxic solid waste, application of this processresulted in a volume decrease of the order of 36.4% while decreasing theleachable lead to levels below the regulatory threshold.

This reduction in volume of the contaminated soil and the solid wastematerial makes the process of the present invention particularlybeneficial for off-site disposal in a secured landfill by cutting downthe costs of transportation and storage space. The process can beaccomplished at a cost-efficient engineering scale on-site or off-sitefor ex-situ treatment of lead-toxic solid wastes. This innovativetreatment technology also offers a great potential for in-situapplication to immobilize lead most economically without generation ofany wastewater or byproducts.

FIG. 3 illustrates schematically the process of the present invention.The lead-contaminated uncontrolled hazardous waste site 10 withlead-toxic wastes is subject to excavation and segregation 20 of wastepiles based on their total lead and TCLP lead contents into (a) heavilycontaminated pile 30A, (b) moderately contaminated waste pile 30B and(c) least contaminated waste pile 30C. The staged soil and solid wastematerial in piles 30A, 30B and 30C is subjected to grinding, shredding,and screening 50 through an appropriately sized mesh sieve. Thescreening yields particles that are usually less than 5 inches indiameter for mixing with gypsum powder 40 in a grizzly that allows auniform coating of gypsum over the soil particles and waste aggregatesduring the grinding, shredding and/or mixing step. Alternatively, asshown by the dashed line, gypsum powder 40 may be added continuously tothe screened solid waste material in prescribed amounts as determinedduring treatability trials. Most of the leachable lead binds chemicallywith gypsum at molecular level to form lead sulfate, which crystallizesinto a synthetic nucleus of mixed calcium anglesite and pure anglesiteminerals identified in the treated material by chemical microscopytechniques.

The gypsum-coated waste particles and aggregates are then transported ona belt conveyor 70 or other conveying means to an area where aneffective amount of phosphoric acid solution 80 of specified strengthsin water 90 is added or sprayed just prior to thorough mixing in a pugmill 100 (or other mixing means). The temperature of the phosphoricsolution is preferably maintained above 30° F. to prevent it fromgelling. The treated soil and wastes are subject to curing 110 anddrying 120 on a curing/drying pad, or may less preferably be cured anddried using thermal or mechanical techniques. The end product of theprocess passes the Paint Filter Test. During the curing time of aboutfour hours, various “super-hard phosphate” mineral species, such ascalcium-substituted hydroxy lead-Apatites and mixed calcium-leadphosphate-sulfate mineral species, are formed in treated waste media130. Crystals of these mineral species (in early stages of development)have been identified in the treated soil materials and solid wastes bygeo-chemical and microscopy techniques like PLM and SEM.

The proportions of waste materials and reagents used in the process maybe varied within relatively wide limits. For example, the amount ofgypsum powder should be sufficient to produce lead sulfate incontaminated solid or solid waste material. In addition, the amount ofphosphate-supplying reagent is prescribed in an amount sufficient toproduce mineral species such as hydroxy-lead apatite in contaminatedsoil or solid waste material during a relatively short curing time of 4hours, usually ranging from about 3 to about 5 hours. Further drying ofthe treated material may take 24 to 96 hours, but has not been requiredin any application to date. Table II documents the optimum curing timeof 4 hours for the process. In all instances, the leachable lead asmeasured by the EP Toxicity Test Procedure was found below 0.6 mg/l andthe differences between analytical values below this level onestatistically insignificant.

TABLE II DOCUMENTATION OF OPTIMUM CURING TIME USING EP TOXICITY TESTCRITERIA FOR LEAD FIXATION EP Toxic Pb Concentration in mg/l EP Toxic Pbfound Waste in processed sample (Untreated at a Curing Time of MatrixSample) 4 Hrs. 48 Hrs. 96 Hrs. Catergory mg/l mg/l mg/l mg/l Pb ToxicSoil A 495 0.4 0.4 0.6 Pb Toxic Soil B  46 0.3 0.2 0.2 Pb Toxic Soil C520 0.3 0.5 0.5

The amount of the gypsum powder and the phosphoric acid employed will bedependent on the amount of contaminant present in the soil, initialcharacteristics of the solid waste material, whether the material isin-situ or is excavated and brought to an off-site facility fortreatment; the same is true for other sulfate compounds and phosphatereagents. The following Example I describes various ratios of thechemical reagents for application to the excavated lead-contaminatedsolid wastes in order to render the leachable lead substantiallyinsoluble; i.e., to reduce the leachable lead to levels below 5.0 mg/lby EP Toxicity Test lead and TCLP Test criteria now in force undercurrent land-ban regulations.

When the present invention is used to treat radionuclides and otherradioactive materials, the amounts of treatment chemicals added are afunction of the contaminated host matrix geochemistry, the concentrationof radionuclides in the host matrix, and the presence of potentialinterferences that could inhibit the reactions, and the geotechnicalproperties of the host material. A preferred rate of TGPA addition is inthe range of 0.1 to 20% by weight of the matrix to be treated. Preferredwater content will also vary with the characteristics of the hostmaterial to be treated, but should be in the range of 5% to 50% byweight. Water content may affect the rate of reaction with lower watercontent requiring longer reaction periods and increased need forsupplemental mixing. Higher water content, on the other hand, mayadversely impact subsequent material handling, and volume reductionresults. Water supplied to an excess will yield a material that willcontain free liquids. In these cases, the treated material should beallowed to react for a longer period of time to permit a decrease inmoisture content by capillary drying and/or evaporation. In someinstances, dewatering or other drying techniques may be used to form amaterial that contains no free liquids.

When TGPA is not utilized as the group two treatment chemical reagent,other compounds that provide soluble phosphates, or phosphates that canbe solubilized may be substituted. The phosphates may be applied in aliquid form or as a solid. Prior to employing the process of the presentinvention at a site, laboratory tests should be conducted to determinethe amounts of group one and group two treatment chemicals that will beneeded for the contaminated matrix that is to be treated. Identificationof carbonates, borates, sulfates, silicates and/or phosphates in thehost material will facilitate the selection of the optimum quantities oftreatment chemicals.

Temperature and Pressure

Ambient temperature and pressure may be used for the disclosed treatmentprocess, permitted the operations of the feeding and mixing equipmentallow such. Under sub-freezing conditions, phosphoric acid may be heatedto 50° F. to prevent it from gelling and in order to keep it in apumpable viscosity range.

Treatment System Design

The treatment may be performed under a batch or continuous system ofusing, for example, a weight-feed belt or platform scale for themetal-hazardous waste materials and a proportionate weight-belt feedsystem for the dry ingredient or ingredients and powders of at least oneof the groups. A metering device, e.g., pump or auger feed system, mayinstead, or additionally, be used to feed the ingredients of at leastone of the groups. The same equipment used for treating metal-hazardouswaste material is used for treating soils and waste materialscontaminated with radionuclides and other radioactive substances.

EXAMPLE 1

Single Step Mixing of Treatment Chemicals A lead contaminated soil froma battery cracking, burning, and recycling abandoned site was obtainedand treated with group one and group two chemicals in one single step atbench-scale. The contaminated soil contained total lead in the range of11.44% to 25.6% and TCLP lead in the ranged of 1781.3 mg/l to 3440 mg/l.The bulk density of contaminated soil was nearly 1.7 g/ml at moisturecontent of 10.3%. The contaminated soil pH was 5.1 with an oxidationreduction potential value of 89.8 mV. To each 100 g lot of leadhazardous waste soil, sufficient amounts of group one and group twotreatment chemicals and reagents were added as illustrated in Table III,in order to render it nonhazardous by RCRA (Resource Conservation andRecovery Act) definition.

TABLE III TCLP Test Run Treatment Additive(s) Lead(mg/′) I  5% lime, 5%gypsum, 10.2% phosphoric 0.5 II 12% phosphoric, 10% potassium sulfate2.2 III 12% phosphoric, 10% sodium sulfate 3.5 IV 15% TSP 3.7 V 12%phosphoric, 10% Portland Cement I 0.2 VI 12% phosphoric, 10% PortlandCement II 0.9 VII 12% phosphoric, 10% Portland Cement III 0.3 VIII 12%phosphoric, 10% gypsum 4.6 IX 15% TSP, 10% Portland Cement 0.1 X 15%TSP, 10% Portland Cement II 0.2 XI 15% TSP, 10% Portland Cement III 0.2XII 15.1% phosphoric 3.6 XIII 10% trisodium phosphate, 10% TSP 1.2 XIV 6.8% phosphoric, 4% TSP 4.5 XV 10% gypsum 340 XVI 12% phosphoric, 5%lime 0.9 Control Untreated Check 3,236.0

It is obvious from TCLP lead analyses of fifteen test runs that thesingle step mixing of at least one component of either or both group oneand group two treatment chemicals is very effective in diminishing theTCLP lead values. In test run I, mixing of lime and gypsum from groupone additives and phosphoric from group two decreased the TCLP lead tolevels below 1 mg/l from 3440 mg/l with a curing time of less than 5hours. Although the treatment chemicals of group two are more effectivein decreasing the TCLP lead than the treatment chemicals of group one,as illustrated by the comparison of test runs XII and XV for this wastesoil, but the combined effect of both groups is even more pronounced indecreasing the leachable lead. Results of these bench-scale studies wereconfirmed during engineering-scale tests. Single step mixing of 5% lime,11.76% phosphoric acid and 15% water in a 2000 g hazardous soildiminished the TCLP lead values form 3440 mg/l to 0.77 mg/l in less than5 hours. Likewise, single step mixing of 300 g Triple Super Phosphate(TSP), 200 g Portland Cement (PC) and 300 ml water in 200 g hazardoussoil decreased the TCLP lead to levels below 0.3 mg/l within arelatively short curing time. Single step mixing of both groups oftreatment chemicals can dramatically reduce treatment costs making thisinvention highly attractive and efficient for commercial use.

The first advantage of using lime and phosphoric acid combination overthe use of TSP and PC is that in the former a volume decrease of 6% wasrealized when compared to the original volume of untreated material. Inthe later case, a volume increase of 37% was measured due to hydrationof cement. The second advantage of using phosphoric and lime combinationis that the mass increase is less than the mass increase when TSP and PCare added. Quantitatively, the mass increase in this hazardous wastesoil treatment was approximately 16.7% due to combination of lime andphosphoric whereas the mass increase was about 40% due addition of TSPand PC. And therefore, those skilled scientists and engineers learningthis art from this patent, must make an economic judgment for each leadcontaminated process material and waste stream which chemical quantityfrom each group would be most effective in rendering the treatedmaterial non-hazardous.

The third advantage in using lime and phosphoric over the use of TSP andPC is that the former does not change in physical and mechanicalproperties of original material and if a batch fails for shortage oftreatment chemicals, it can be retreated rather easily by adding more ofthe treatment reagent. The material treated with PC hardens and may forma monolith which is difficult to retreat in case of a batch failure.

EXAMPLE 2 Interchangeability of Two Step Mixing Method

In the lead contaminated soil from the abandoned battery recyclingoperations, the treatment chemicals of either group can be added firstand mixed thoroughly in an amount sufficient to decrease the TCLP leadbelow the regulatory threshold. Two step mixing method of the group oneand group two treatment additives is as effective as single step mixingof same quantity of treatment chemicals selected from group one andgroup two.

Table IV illustrates data that confirm that the application of group onetreatment chemicals in step I is about as effective as application instep II. The same is true for group two treatment chemicals. Thus, thetwo steps are essentially interchangeable. The reversibility of thesteps according to the present invention make it very flexible foroptimization during commercial use, scaling up and retreatment of anybatches that fail to pass the regulatory threshold criteria.

TABLE IV TREATMENT ADDITIVES TWO STEP MIXING METHODS TCLP TEST TOTALLEAD RUN STEP I STEP II LEAD mg/l I 10% gypsum & 2% 12% phosphoric acid20.8 1.8 lime (Group I) (Group II) II 12% phosphoric 10% gypsum & 2%24.4 1.9 (Group II) lime (Group I) III 10% gypsum 10.6% phosphoric 24.43.4 (Group I) (Group II) IV 10.6% phosphoric 10% gypsum 22.4 3.5 (GroupII) (Group I) Single Step Mixing Method V 10% gypsum and 12% phosphoric23.6 3.5 Untreat- Control/Check 23.1 3440 ed

EXAMPLE 3 Retreatability and Single Step Mixing

A sample of hazardous cracked battery casings of ½″-1″ size containing14% to 25.2% total lead and about 3298 mg/l of TCLP was obtained forseveral test runs of the invention to verify the retreatability ofbatches that fail because of the insufficient dose of treatment chemicaladded. The results of initial treatment and retreatment are presented inTable V and compared with single step mixing treatment additives fromboth groups. About 200 g of hazardous material was treated with 10.5%phosphoric acid, 2.5% gypsum and 1.25% lime, all mixed in one singlestep. The TCLP lead was decreased from 3298 mg/l to 2.5 mg/l as a resultof single step mixing in test run V (TABLE V).

When the amount of additive from group two was less than the optimumdose needed, the TCLP lead decreased from 3298 mg/l to: (i) 1717 mg/lwhen 4.2% phosphoric and 1% lime were added during step I and IIrespectively, and (ii) 2763 mg/l when 4.2% phosphoric and 5% gypsum wereadded, compared to untreated control.

Since the TCLP lead did not pass the regulatory criteria of 5 mg/l,treated material from test runs I and II were retreated during test runsIII and IV, respectively, using sufficient amounts to phosphoric acid(an additive from group two) in sufficient amount to lower the TCLP leadto 2.4 mg/l and 2.5 mg/l, respectively. Furthermore, this exampleconfirms that lime is more effective in decreasing TCLP lead than gypsumamong different additives of group one. And as a result, the requirementof group two treatment reagent is lessened by use of lime over gypsum.The example also illustrates that one or more compounds of the samegroup can be used together to meet the regulatory threshold limit.

TABLE V TREATMENT ADDITIVES TWO STEP MIXING METHODS TCLP Lead Test RunStep I Step II mg/l I 4.2% phosphoric 1% lime 1717 II 4.2% phosphoric 5%gypsum 2763 Untreated 3296 Control Retreatment (Single Step Mixing)Method III-I 6.8% phosphoric 2.4 IV-II 8.5% phosphoric 3.5 Single StepMixing V 10.5% phosphoric, 2.5% gypsum, 2.5 1.25% lime

EXAMPLE 4 Wide Range of Applications and Process Flexibility in CuringTime Moisture Content and Treatment Operations

TABLE VI illustrates different types of waste matrix that have beensuccessfully treated employing the one step and two step mixingtreatment additives from group one and group two. For these diversewaste types and process materials, total lead ranged form 0.3% to 23.5%.This example discloses the flexibility and dynamics of the treatmentprocess of the invention in rendering non-hazardous, by RCRA definition,a wide range of lead-hazardous and other metal-hazardous materialswithin a relatively short period of time, usually in less than 5 hours.It is expected that this process will also render bismuth, cadmium,zinc, chromium (III), arsenic (III), aluminum,, copper, iron, nickel,selenium, silver and other metals also less leachable in these differenttypes of wastes. The moisture content of the waste matrix is notcritical and the invented process works on different process materialsand waste types independent of the moisture content. The treatmentoperations can be carried out at any level—bench, engineering, pilot andfull-scale—on relatively small amounts of hazardous waste material inlaboratory to large amounts of contaminated process materials, soils,solid wastes, waste waters, sludges, slurries and sediments outdooron-site. The process is applicable in-situ as well as ex-situ.

TABLE VI UNIVERSE OF APPLICATION FOR THE INVENTION MACTITE TREATMENTPROCESS LEAD LEACHABLE LEAD (mg/l) CONTAMINATED TREATMENT TOTAL BeforeAfter VOLUME WASTE TYPE ADDITIVE LEAD % Treatment Treatment DECREASE OLDDIRT 3.4% Phosphoric 2.2 164.4 1.5 16.7 WASTE WITH BROKEN 8.1% Lime 2.7197.5 ND (<.5) BATTERY CASING 1% Gypsum and 3.4% Phosphoric SLAG-LEADSHELTER 10.2% Phosphoric 6.6 21.3 2.0 LEAD-BIRD SHOT 16% Phosphoric 16.13720 ND (<.5) 14% Lime and 30% Gypsum LEAD-BUCK SHOT 16% Phosphoric 11.41705 ND (<.5) 14% Lime and 28% Gypsum BATTERY CASINGS 5% Gypsum 12 2880.6 0 ORGANIC HUMUS SOIL 0.5% Lime 1.9 23.2 ND (<.5) 29 2.0% Phosphoric50:50 MIXTURE OF 4% Gypsum 0.5 687 0.7 3.3 CASINGS AND SAND 4%Phosphoric 422.2 0.95 23.6 SOLID WASTE SOIL 3% Lime 23.5 12.0 6.0Contaminated With 12% Phosphoric Tetraethyl lead SOIL CONTAMINATED 10%Gypsum 4.74 590 13.7 WITH LEADED 6% Phosphoric GASOLINE 3% Lime 3.2 2131.6 5.1% Phosphoric CARBON WITH 4.7% Phosphoric 12.6 105.6 0.5 LEADDROSS WIRE FLUFF 1.7% Phosphoric 0.3 19 0.7 WIRE CHIP 0.75% Phosphoric0.4 28 ND (<.2) LAGOON SEDIMENT 0.6% TSP 0.3 3.9 0.23 0.5% Phosphoric5.6 0.3 RCRA ORGANIC SLUDGE 0.6% Phosphoric 9.4 580 ND (<.5) 10% GypsumFILTER CAKE 8.5% Phosphoric 2.9 245.3 1.1 GRAVEL 5% Gypsum 0.16 7.5 0.52.2% Phosphoric ROAD GRAVEL 10% Gypsum 0.34 46 ND (<.5) 8.4% PhosphoricMIXTURE OF BATTERY 2.5% Gypsum 1.3 75 0.6 19.6 CASINGS (SOLD WASTE) 3.4%Phosphoric AND SOIL INDUSTRIAL WASTE 1 g Lime 2.75 91 0.7 (B) 3.4%Phosphoric INDUSTRIAL PROCESS 3.4% Phosphoric 1.3 61 ND (<.5) MAT. (G)SOIL (B) 3.4% Phosphoric 4.1 129.5 0.6 25.6 SOIL (S) 50% Gypsum 11 <0.01SOIL (O) 1.3% Phosphoric 0.38 34.6 ND (<.5) SOIL (C) 5% Lime 11.78 130.60.33 8.5% Phosphoric BATTERY CASINGS 5% Gypsum 2.5 110.1 1.9 3.4%Phosphoric GRAY CLAY SOIL 5% Trisodium 2.2 46.6 0.2 Phosphate

EXAMPLE 5

Nearly twenty (20) different chemicals and products from various vendorsand supply houses were screened for chemical fixation of leachable leadin hazardous solid waste samples. Only six (6) of these treatmentschemicals were found effective in decreasing the leachable lead asmeasured by: (1) the EP Toxicity Test and (2) the TCLP Test. Table VIIpresents a summary of leachable lead found in untreated and treatedwaste samples allowed to cure for a minimum of 4 hours after treatmentwith at least one of the effective chemicals. Treatment chemicals foundrelatively ineffective for lead fixation included a variety ofproprietary products from American Colloid Company and Oil Dri,different sesquioxides like alumina and silica, calcium silicate, sodiumsilicate, Portland cement, lime, and alum from different vendors.Results for these ineffective chemicals are not shown in Table VII.

TABLE VII RELATIVE EFFECTIVENESS OF VARIOUS TREATMENT CHEMICALS SCREENEDTO DECHARACTERIZE THE LEAD-TOXIC SOLID WASTES Leachable Lead in mg/lTreatment Chemical (Step) Toxicity Test EP TCLP Test I. UntreatedControl 221.4 704.5 II. Single Treatment Chemical (One Step Treatment)a. Sulfuric Acid (I) 11.7 39.8 b. Phosphoric Acid (I) 1.0 5.9 c.Superphosphate Granular (I) 2.7 11.4 d. Liquid Phosphate Fertilizer (I)19.4 64.3 e. Gypsum Powder (I) 24.9 81.8 f. Sodium Phosphate (I) 28.793.9 III. Two Step Treatment g. Sulfuric (I) & Lime (II) 20.6 68.1 h.Gypsum Powder (I) & Alum (II) 3.9 15.3 i. Sodium Phosphate (I) & 3.112.6 Phosphoric (II) j. Gypsum (I) & Phosphoric (II) N.D.* 1.6 IV. ThreeStep Treatment k. Gypsum (I), Alum (II) & 12.8 43.3 Sodium Phosphate(III) l. Gypsum (I), Phosphoric (II) & N.D.* 1.4 Sodium Phosphate (III)*N.D. means non-detectable at <0.50 mg/l.

Evaluation of a single treatment chemical in one step reveals thatphosphoric acid was most effective in fixation of leachable leadfollowed by granular super-phosphate, a fertilizer grade productavailable in nurseries and farm supply houses. However, neithertreatment effectively treated leachable lead to the USEPA treatmentstandard of 5.0 mg/l by TCLP methodology.

Although both phosphoric acid and granular superphosphate were effectivein meeting the now obsolete EP Toxicity Test criteria at 5.0 mg/l, thistest has been replaced by TCLP Test criteria for lead of 5.0 mg/l.Single application of the phosphoric acid, granular superphosphate orany other chemical was short of meeting the regulatory threshold of 5.0mg/l by TCLP Test criteria for lead.

In a two-step treatment process, application of gypsum during Step I andtreatment with phosphoric acid in Step II resulted in decrease ofTCLP-lead consistently and repeatedly below the regulatory threshold of5.0 mg/l. The results of this two-step treatment process utilizinggypsum in Step I and phosphoric acid in Step II are most reliable andhence, the two-step process may be applied to a wide variety of leadcontaminated wastes as exhibited in Example II.

A three-step process, as set forth in Table VII, was not perceived to beas economically viable as a two-step treatment process, despite itsability to reduce lead levels in satisfaction of the TCLP Test criteria.A process that employs the beneficial combination of treatment firstwith a sulfate compound and then with a phosphate reagent in accord withthe present invention, in combination with one or more additionaltreatment steps, may nevertheless be within the scope of the invention.

In order to illustrate the relative proportions of two chemicals, e.g.,gypsum and phosphoric acid, needed for treatment of lead-toxic wastes,three soil samples from a lead contaminated test site were processedusing the present invention, in which gypsum powder was used in thefirst step, and phosphoric acid solution in water at concentrations ofabout 7, 15 and 22 percent by weight in the second step. The soil wasmeasured for lead content in accordance with the EP Toxicity Test beforeand after treatment. A level of leachable lead below 5 mg/l wasconsidered non-hazardous according to this procedure. During these testruns, the EP Toxicity Test criteria were in force for treated wastematerial. The results of these tests are set forth in Table VIII:

TABLE VIII EFFECTIVENESS IN FIXATION AND STABILIZATION OF LEACHABLE LEADIN LEAD TOXIC SOILS EP TOXIC LEAD PROCESS STEPS TEST REULTS Soil SampleGypsum Phosphoric Before After (Lead-toxic Step I Step II TreatmentTreatment waste) (g/kg soil) (g/kg soil) mg/l mg/l 1. Low lead 20 10 8<0.1 contamination 2. Moderate 30 20 61 <0.1 contamination 3. Highlead40 30 3,659 1.7 contamination

The foregoing results demonstrate that the process of the presentinvention was effective in all three samples, representing 3 differentlevels of lead contamination. The process is flexible and is usuallyoptimized during bench scale treatability studies for each waste type toimmobilize the leachable lead and to decharacterize or transform thelead-toxic waste into non-toxic solid waste acceptable to TSD facilitiesunder current land ban regulations. A net reduction of 36.4% in wastevolume through use of the instant process has been observed. Typicalvolume reductions are set forth in Table IX.

TABLE IX CHANGES IN SOLID WASTE VOLUME AS A RESULT OF TREATMENT WITH THETWO-STEP PROCESS SOLID WASTE VOLUME Final (After Decrease in SOLID WASTEInitial (Before Application of Waste MATERIAL Application of Process andVolume (Treatment Scale) Process) Curing) (%) 1. Low toxic soil 3,85Ocu. yd. 2,450 cu. yd. 36.4 (full scale) 2. Lead toxic Solid Waste (BenchScale) Test Run I   106.1 cu. in.   81.51 cu. m. 23.0 Test Run II   22.0cu. in.   17.3 cu. in. 21.4

The most profound effect of the process of the present invention is at astructural level, where the break-down of granular aggregates isassociated with a loss of fluffiness and a decrease in pore space andincreased compaction due to physical, mechanical and chemical forces atdifferent levels. At a molecular level, phosphoric acid breaks down theminerals containing carbonates and bicarbonates, including cerussites,in stoichiometric proportions. Soon after the addition of phosphoricacid to a solid waste containing cerussites, extensive effervescence andfrothing becomes evident for several minutes and sometimes for a fewhours. The phosphoric acid breaks down the acid sensitive carbonates andbicarbonates leading to the formation of carbon dioxide, water andhighly stable and insoluble sulfate and phosphate mineral compounds.Thus, structural changes due to interlattice reorganization as well asinterstitial rearrangement in waste during processing are associatedwith an overall decrease in waste volume. Depending on the extent ofcarbon dioxide loss from the breakdown of carbonates and bicarbonatespresent in the lead-toxic solid waste, the process may lead to a slightloss of waste mass as well. Water generated during the chemicalreactions is lost by evaporation, which further decreases the mass andvolume of the treated solid wastes and soils.

The cost of the process of the present invention is moderate to low,depending upon (i) waste characteristics, (ii) treatment system sizing,(iii) site access, (iv) internment of final disposition of treatedmaterial and (v) site support requirements. The costs of treatment anddisposal are presently on the order of $115 per ton of lead-toxic waste,as compared to off-site conventional treatment and disposal costs ofover $250 per ton if no treatment in accord with the invention had beenperformed. Moreover, recent land ban regulations would prohibit thedisposal of all lead-toxic wastes in landfills. The foregoing Examplemakes clear that the process of the present invention provides anefficient technology that is economically attractive and commerciallyviable in meeting regulatory criteria for landfills.

EXAMPLE 6

The process of the present invention was applied on bench scale to fivedifferent lead-toxic waste materials that were characterized for totallead, TCLP-lead, moisture content and pH before and after treatment. Acuring time of 5 hours was allowed for completion of the treatmentprocess. The results compiled in Table X exhibit the profound effects ofthe process in decreasing the TCLP lead in a wide range of lead-toxicsoils and solid wastes containing total lead as high as 39,680 mg/kg andTCLP lead as high as 542 mg/l. In each of the five cases, the instantprocess immobilizes the leachable lead to levels below the regulatorythreshold of 5 mg/l set by the TCLP Test criteria for lead currently inforce under the land ban regulations of the United States EnvironmentalProtection Agency.

TABLE X TYPICAL CHANGES IN SOLID WASTE CHARACTERISTICS DUE TO PROCESSEFFECTS MEASURED VALUES SOLID WASTE Before After TreatmentCHARACTERISTICS Treatment & Curing I. Lead-toxic SW-A Total lead, %1.442 1.314 TCLP-Lead, mg/l 542.0 2.0 Moisture, % 23.0 33.0 pH, S.U. 8.14.8 II. Lead-toxic SW-B Total lead, % 0.847 0.838 TLCP-Lead, mg/l 192.02.4 Moisture, % 27 36 pH, S.U. 8.0 5.3 III. Lead-toxic SW-C Total lead,% 3.968 3.066 TLCP-Lead, mg/l 257.6 1.0 Moisture, % 10.0 18.1 pH, SU.7.2 4.5 IV. Lead-toxic SW-D Total lead, % 2.862 2.862 TLCP-Lead, mg/l245.3 0.38 Moisture, % 71.6 84.1 pH, SU 8.1 6.3 V. Lead-toxic SW-E Totallead, % 0.16 0.12 TLCP-Lead, mg/l 7.5 1.87 Moisture, % 12.3 23.0 pH,S.U. 7.0 5.4

It is obvious from Table X that the instant process operates over a widerange of moisture and pH conditions. It is associated with 8 to 11% risein moisture content. The end product of the treatment process maycontain moisture in a typical range of 18% to 36% on a dry weight basis.The end product passes the Paint Filter Test for solids and there arenot other byproducts or side streams generated during the process. Thetreated solid waste is cured in 4 to 5 hours and may be allowed to dryfor 2 to 3 days after treatment for loss of unwanted moisture prior tofinal internment and disposition. This time is sufficient for the TCLPTests to be completed as part of the disposal analysis under land banregulations enforced by the USEPA.

It is necessary to establish the quantities of gypsum and phosphatereagent on a case-by-case basis, because the consumption of thesematerials will depend not only upon the initial lead level in the wasteor soil, but also upon other waste characteristics such as cationexchange capacity, total buffering capacity, and the amounts ofcarbonates and bicarbonates present, among others. Bench scaletreatability studies for each solid waste considered will be necessaryto determine the optimum levels of the materials that are employed. Thetreatability studies are designed to optimize the amount and grade ofgypsum powder (or other sulfate compound) needed during step I, and theamount and concentration of phosphoric acid (or other phosphatecompound) needed in step II for cost-effective operation of thetreatment system. Those skilled in the art are knowledgeable of suchbench studies, which are usually carried out as precursors to full scaletreatment.

Several series of studies were performed on host matrices containingleachable and soluble radionuclides and other radioactive substancesusing the present invention.

EXAMPLE 7

Sample material from a site in the eastern United States washomogeneously mixed in a container. The material consisted of silts,clays, sand and gravel mixed with glass, nails, rocks and debris. Thematerial was collected from an environmental restoration project wheresite efforts focused on excavation, packaging, transportation anddisposal of Thorium contaminated soil and materials from beneathresidential homes.

Three 300 g sub-samples of untreated material were prepared from thesample material with the materials in each of the sub- samples sized toless than ⅜ inch and suitable for USEPA SW-846 Method 1311 (TCLP)extraction. Sample 1 (US-1) was extracted using TCLP fluid No. 1, Sample2 (US-2) was extracted using TCLP fluid No. 2, and Sample 3 (US-3) wasextracted using laboratory grade deionized (“DI”) water as the onlymodification to the EPA method. This soil characterization step wasconducted for purposes of determining the most harsh extractionconditions for the untreated material. TCLP fluid No. 1 was preparedwith glacial acetic acid and 1N NaOH with an end pH of 4.93+/−0.05 S.U.TCLP fluid No. 2 was prepared with glacial acetic acid and deionizedwater with an end pH of 2.88 +/−0.05 S.U. The laboratory grade DI waterhad a pH of 6.82+/−0.05 S.U.

After tumbling 100 g of the 300 g sub-sample in 200 ml of extractionfluid for eighteen (18) hours at 30+/−2 rpm in a longitudinal rotaryTCLP agitator, the extracts were decanted from the settled solids,filtered as per the method, and then placed in Marinelli containers.Radionuclide leachability was determined by conducting total gammaspectroscopy analysis on each extract in accordance with acceptedquantification methods using a Nuclear Data Genie Model ND9900 GammaSpectrometer integrated with a DEC Micro VAX II computer. Each extractwas counted for sixteen (16) hours. All results presented below are inthe units of picocuries per liter (pCi/l).

TABLE XI EASTERN UNITED STATES UNTREATED SAMPLE MATERIALCHARACTERIZATION    US-1    US-2    US-3   Untreated   Untreated  Untreated Radionuclide TCLP Fluid 1 TCLP Fluid 2 Deionized WaterPb-210   329 ± 30   173 ± 45   175 ± 37 Bi-211 2,751 ± 736  3,360 ± 797 3,451 ± 560 Bi-214   772 ± 93  1,002 ± 120  1,017 ± 106 Pb-214   810 ±350   910 ± 242   966 ± 202 Fr-223 2,183 ± 660  3,768 ± 73  3,228 ± 531Ra-223   939 ± 404  1,514 ± 383   714 ± 148 Ra-224 1,551 ± 503  1,772 ±358  1,868 ± 321 Ra-226 1,090 ± 167  1,294 ± 162  1,352 ± 156 Ac-227  213 ± 20   243 ± 54   173 ± 31 Th-227   533 ± 163   921 ± 179   788 ±131 Th-228 8,335 ± 1014 16,490 ± 12 13,170 ± 1,371 Pa-231 1,136 ± 476 1,764 ± 467  1,490 ± 307 Th-234   22 ± 6    19 ± 13    10 ± 9 U-235  190 ± 22   313 ± 38   281 ± 29

As shown by the gamma spectral analysis of each extract, TCLP fluid No.2 was identified as the most rigorous extraction fluid for the soilmaterial, primarily because of leachable Thorium and Uranium levels.This fluid was then selected to be used for extraction of the treatedsamples for the remainder of the studies.

In the second portion of the study, two (2) 300 g samples were preparedfrom the eastern U.S. sample material and labeled as TS-1 and TS-2. Eachsample was placed in a laboratory beaker and 35 ml of deionized waterand 5% (TS-1) and 10% (TS-2) by weight TGPA were added. The contents ineach of the beakers were then mixed by folding with a laboratory spatulain order to simulate blending achievable using full-scale methods in thefield. The samples were then allowed to react overnight. Each beaker wasthen sub-sampled, material particles sized to less than ⅜ inch, andprepared for USEPA SW-846 Method 1311 (TCLP) extraction using 100 g oftreated sub-sample material and 2000 ml TCLP Fluid No. 2. Table XIIpresents the data from the gamma spectral analysis with all unitsreported as pCi/l. The results from Table XI for untreated materialsextracted using TCLP Fluid No. 2 were used as a control and are shown inthe fourth column.

TABLE XII EASTERN UNITED STATES SAMPLE MATERIAL TREATED WITH DJ WATERAND TGPA TCLP EXTRACTION FLUID NO. 2 RESULTS Radio- TS-1 TS-2 US-2nuclide 5% TGPA 10% TGPA TCLP Fluid No. 2 Pb-210 <MDA* <MDA  173 ± 45Bi-211 <MDA <MDA 3,360 ± 797 Bi-214 <MDA <MDA 1,002 ± 120 Pb-214 <MDA<MDA   910 ± 242 Fr-223 <MDA <MDA 3,768 ± 73  Ra-223 <MDA <MDA 1,514 ±383 Ra-224 <MDA <MDA 1,772 ± 358 Ra-226 <MDA <MDA 1,294 ± 162 Ac-227<MDA <MDA  243 ± 54 Th-227 <MDA <MDA   921 ± 179 Th-228 <MDA <MDA 16,490± 12  Pa-231 <MDA <MDA 1,764 ± 467 Th-234 <MDA <MDA   19 ± 13 U-235 <MDA<MDA  313 ± 38 *<MDA = less than the calculated Minimum DetectableActivity for the counted sample MDA is the smallest amount of activitythat can be detected in a sample. Data from TS-1 was corroborated by asecond laboratory on duplicate sample extract for QA/QC data validationpurposes.

As indicated by the data from Tables XI and XII, TGPA substantiallyreduces the leachability of radionuclides in soil as determined by USEPASW-846 Method 1311 (TCLP) extraction with fluid No. 2 and gamma-spectralanalysis of resultant extract. It should be noted that the soil samplematerials were not sized to less than ⅜ inch until after the TGPA anddeionized water were mixed and allowed to cure overnight.

The leaching of Thorium, its decay-daughters, and other radionuclidesfrom untreated material was effectively reduced by the addition of TGPAto the material. The treated material was moist after curing overnight,but contained no free liquids. After exposure to the air for forty-eight(48) hours, the treated material was dry and crumbly with nonuniformcohesivity. Volume reduction was observed, but not quantified.

EXAMPLE 8

In another study, samples of the untreated material used in Example 7were mixed with TGPA and other compounds. For this study, gypsum,calcium oxide, triple superphosphate (TSP), and TGPA were selected basedupon a generally desired pH range of the end product. Four 300 g sampleswere prepared: TS-3=35 ml DI water+8% gypsum+5% TGPA; TS-4=35 ml DIwater+9% calcium oxide+8% TGPA, TS-5=35 ml DI water+3% calcium oxide+5%TGPA; and TS-6=45 ml DI water+10% TSP+1.6% calcium oxide.

Treatment samples received variable amounts of water so that aftermixing, the consistency of the mixtures was uniform for all of thesamples and there were no free liquids. The water assisted in thedispersement of the reagent and calcium oxide hydration; and hence, thedisassociation of the phosphate to a soluble form. Additional water wasrequired in TS-6 because of the solid reagent forms and the hydrationdemand of CaO in the presence of dry TSP.

Table XIII presents the data from USEPA SW-846 Method 1311 (TCLP)extracts of TS-3, TS4, TS-5, and TS-6 analyzed by totalgamma-spectroscopy in accordance with procedures outlined in Example 7.All samples were analyzed with TCLP fluid No. 2 (acetic acid+water witha pH of 2.88+/−0.05 S.U.).

TABLE XIII EASTERN UNITED STATES SAMPLE MATERIAL TREATED WITH OTHEREMBODIMENTS TCLP EXTRACTION FLUID NO 2 RESULTS Radionuclide TS-3 TS-4TS-5 TS-6 Pb-210 <MDA <MDA <MDA <MDA Bi-211 <MDA 180 ± 69 296 ± 106 <MDABi-214 <MDA  55 ± 23 75 ± 29 <MDA Pb-214 <MDA <MDA 50 ± 50 <MDA Fr-223<MDA <MDA <MDA <MDA Ra-223 <MDA 245 ± 97 84 ± 34 <MDA Ra-224 <MDA <MDA<MDA <MDA Ra-226 <MDA <MDA 122 ± 114 <MDA Ac-227 <MDA <MDA 286 ± 47 <MDA Th-227 <MDA <MDA 552 ± 31  <MDA Th-228 <MDA <MDA <MDA <MDA Pa-231<MDA <MDA <MDA <MDA Th-234 <MDA <MDA 139 ± 53  <MDA U-235 <MDA <MDA 79 ±35 <MDA *<MDA = less than the calculated Minimum Detectable Activity(MDA) for the counted sample Data from samples TS-3 and TS-6 wascorroborated by a second laboratory on duplicate sample extracts forQA/QC data validation purposes.

As evidenced by the data, the treatment regimes utilizing gypsum+TGPA,calcium oxide+TGPA, and triple superphosphate (TSP)+calcium oxideresulted in the reduction of nuclide leachability. Each of the treatmentregimes provided soluble phosphates, or phosphates that were solubilizedby pH manipulation in the presence of a fluid. Each of the treatmentsresulted in the formation of Apatites within the host material, withmineral crystal nucleation chemically incorporating the radionuclides.

EXAMPLE 9

The tests in Example 9 were performed to study the volume change ofmaterials treated by the process of the present invention. In Example 9,soil volume was examined prior to and after the addition of TGPA.Because of the difficulty in examining volume changes due to variedconditions, geometric configuration, and chemical properties of materialdiffering between pre- and post-treatment, a special device wasconstructed to account for changes in density, moisture content, andgeotechnical properties.

The test apparatus used for measuring the volume consisted of aremovable stainless steel cylindrical cup with a flat bottom (“thecup”). The cup had a 10.3 cm inside diameter and a 29.6 cm inside heightand mounted vertically to the base of the test apparatus. Mounted abovethe cup on the apparatus frame was a pneumatic piston with a 1.4 cmthick plate fixed to the piston shaft. When activated with compressedair, a 10.2 cm diameter close-tolerance plate fixed to the piston shaftextended downward and into the open end of the cup. Compressed airoperated the piston and was adjusted with a valve so that from 1 to 100psi could be exerted on soil placed within the cup.

The untreated material from Example 7 was used to prepare ten aliquots(of approximately 100 g) which were individually weighed using atop-loading electronic balance (+/−0.01 g). The ten aliquots were thensequentially emptied into the cup. After the addition of each 100 galiquot, the cylindrical cup was placed in the apparatus and the pistonactivated to exert a pressure of 10 psi on the soil column. Thisprocedure was repeated until all ten 100 g aliquots had been added andcompacted. The height of the soil column was then determined bymeasuring from the top of the cup to the top of the plate, correctingfor the plate thickness, and subtracting the total from the insideheight of the cup.

The untreated material was then removed from the cup and placed in alaboratory beaker. Care was taken to ensure all visible material wasremoved and transferred. Water was added to the beaker on a weight basisequal to 12% of the untreated material. TGPA was then added at a dose of5%, also by weight, of the untreated material. The untreated materialand amendments were mixed with a laboratory spatula by folding andallowed to sit overnight.

The treated material was then removed from the beaker and placed in thecylindrical cup in ten stages of approximately 100 g each. The pneumaticpiston was activated at the same 10 psi pressure each time treatedmaterial was added to the cup. After all of the treated material wastransferred and compacted with the apparatus, the resultant columnheight was calculated as previously described. After the material hadbeen allowed to sit for approximately seven (7) days, the volume testwas performed again in the same manner. The results of the study arepresented in Table XIV.

TABLE XIV VOLUME CHANGE OF EASTERN UNITED STATES SAMPLE MATERIAL TREATEDWITH 5% (WT.) TGPA Mass Height Mass Height Mass Height Treated TreatedTreated Treated Untreated Untreated <24 hours <24 hours 7 days 7 daysgrams (cm) (grams) (cm) (grams) (cm) 1003.09 8.2 1074.77 7.4 942.51 6.7

These test results show a total volume reduction of 9.75% after 24 hoursand 22.4% after 7 days, relative to the initial untreated material.

In the next series of studies, sample material from a site in theMidwestern United States was utilized in treatability studies. Thematerial contained small soil grains (with 100% passing through a 9.5 mmsieve) and was comprised of 30% sand, 47% silt, and 23% clay asdetermined by ASTM D-422 (Particle-Size Distribution). The averagedensity of the material was 1.43 g/cc and the material had a moisturecontent of 16 percent by weight and a pH of 6.0 S.U.

As in the previous examples, the sample material was characterized forradionuclides and other radioactive substances. Nuclide leachability wasexamined utilizing the Toxic Characteristic Leaching Procedure (TCLP)extraction procedure (USEPA SW-846, Method 1311). Material was alsosubjected to other leaching tests including the Synthetic PrecipitationLeaching Procedure (SPLP) extraction procedure (USEPA SW 846, Method1312), and a modified version of the TCLP extraction method, wheredeionized water was substituted for the extraction fluid (DI/TCLP).Results of the gamma-spectral, Uranium, and Technetium-99characterization analyses on extraction fluids are presented in TableXV.

TABLE XV UNTREATED MIDWESTERN UNITED STATES SAMPLE MATERIAL RADIONUCLIDELEACHABILITY CHARACTERISTICS USA US-5 US-6 Radionuclide/ Method 1311Method 1312 Modified-1311 Isotope/Item TCLP SPLP DI/TCLP Ra-226 3,644 ±895 3,120 ± 494   556 ± 219 U-235  266 ± 66  190 ± 43   39 ± 25 U238*12,308 ± 969  11,210 ± 92  2,590 ± 45  Pb-212  16 ± 4 <MDA <MDA Th-234  485 ± 138  355 ± 90  228 ± 73 Tc-99  238 ± 11  152 ± 10  235 ± 11 U8,698 ± 68  7,922 ± 65  1,830 ± 32  U, total(ug/l) 17,979 16,375 3,783NOTE: All units in pCi/l, unless indicated *U-238 concentrations werecalculated. <MDA = less than the calculated Minimum Detectable Activity(MDA) for the counted sample

EXAMPLE 10

In this example, four 400 g samples of soil material (TS-7, TS-8, TS-9and TS-10) were prepared from the untreated Midwestern U.S. samplematerial and placed in separate laboratory beakers. Sample TS-7 was usedas a control and mixed only with 120 ml of deionized water. For each ofthe three other samples, 120 ml of deionized water and varying amountsof TGPA were added to each beaker and mixed until a uniform consistencywas achieved: TS-8=120 ml DI water+3% (wt.) TGPA; TS-9=120 ml DIwater+5% (wt.) TGPA; and TS-10=120 ml DI water+10% (wt.) TGPA. When themixing was completed, no free liquids were present.

After sitting overnight, a 100 g sample of treated material was removedfrom each beaker and extracted by USEPA SW-846, Method 1311 (TCLP),using Fluid No. 2, to simulate exposure to acidic landfill leachate. Theradionuclide leachability for each extract was then quantified by gammaspectroscopy. Total Uranium and Technetium-99 tests were also conducted.Uranium-238 was calculated, assuming the total Uranium present was 100%depleted. The levels of leachable radionuclides and other radioactivesubstances in the sample material after treatment are presented below inTable XVI. The results in Table XVI can be compared to the results forsample US-4 in Table XV for reference.

TABLE XVI RADIONUCLIDE LEACHABILITY OF MIDWESTERN UNITED STATES SAMPLEMATERIAL IN USEPA SW-846, METHOD 1311 (TCLP) FLUID NO. 2 EXTRACT AFTERTREATMENT WITH TGPA Radionuclide/ TS-7 TS-8 TS-9 TS-10 Isotope/Item DIWATER 3% TGPA 5% TGPA 10% TGPA Ra-226 3,114 +/− 568 <MDA <MDA <MDA U-235  231 +/− 55 <MDA <MDA <MDA U238*(ug/l) 5,847 +/− 184 54.5 +/− 1.7 51.7+/− 1.7 53.5 +/− 1.7 Th-234   230 +/− 97 <MDA <MDA <MDA Tc-99   213 +/−14.3 67.6 +/− 8.5 55.6 +/− 10.4  3.7 +/− 4.8 U 4,132 +/− 130 38.5 +/−1.2 36.5 +/− 1.2 37.8 +/− 1.2 U, total(ug/l) 8,541 80 75 78 NOTE: Allunits in pCi/l, unless indicated *U-238 concentrations were calculated.<MDA less than the calculated Minimum Detectable Activity (MDA) for thecounted sample

EXAMPLE 11

100 g samples of material treated in Example 10 (TS-7, TS-8, TS-9 andTS-10) were sub-sampled, extracted and analyzed by USEPA SW-846, Method1312 (SPLP), where the extraction fluid utilized simulated acid rain.Each extract was then quantified for radionuclides bygamma-spectroscopy, and total Uranium and Technetium-99 tests wereconducted. Uranium-238 was calculated, assuming the total Uraniumpresent was 100% depleted. The results of the leachable radionuclidesand other radioactive substances in the soil after treatment arepresented below in Table XVII. The results in Table XVII can be comparedto the results for sample US-5 in Table XV for reference.

TABLE XVII RADIONUCLIDE LEACHABILITY IN EPA SW-846, METHOD 1312 (SPLP)EXTRACT AFTER TREATMENT WITH TGPA Radionuclide/ TS-7 TS-8 TS-9 TS-10Isotope/Item CONTROL 3% TGPA 5% TGPA 10% TGPA Ra-226 2,622 +/− 443  233+/− 136 <MDA <MDA U-235   153 +/− 37 <MDA <MDA <MDA U-238* 6,065 +/− 19230.1 +/− 1.0  8.8 +/− 0.1  7.3 +/− 0.1 Th-234   170 +/− 81 <MDA <MDA<MDA Tc-99   210 +/− 15 55.6 +/− 7.8 23.2 +/− 6.5 69.8 +/− 7.6 U 4,286+/− 136 21.3 +/− 0.7  6.3 +/− 0.1  5.2 +/− 0.1 U, total(ug/l) 8,859 4413.9 10.7 NOTE: All units in pCi/l, unless indicated *U-238concentrations were calculated. <MDA = less than the calculated MinimumDetectable Activity (MDA) for the counted sample

EXAMPLE 12

100 g samples of treated soil material in Example 10 (TS-7, TS-8, TS-9and TS-10) were subsampled and extracted by USEPA SW-846, Method 1311with laboratory grade deionized water substituted for the extractionfluid. Although material treated by the invention would never likely beexposed to similar fluid except in the laboratory settings, deionizedwater is considered by many to be a harsh extraction test as leachableionic species will tend to diffuse from zones of high concentration tozones of low concentration. Each DI water extract was then quantifiedfor radionuclides by gamma-spectroscopy, and total Uranium andTechnetium-99 tests were conducted. Uranium-238 was calculated, assumingthe total Uranium present was 100% depleted. The results showing thelevel of leachable radionuclides and other radioactive substances in thesoil after treatment are presented below in Table XVIII for TS-7, TS-8,TS-9 and TS-10. The results in Table XVIII can be compared to theresults for sample US-6 in Table XV for reference.

TABLE XVIII RADIONUCLDE LEACHABILITY IN EPA SW-846, MODIFIED METHOD 1311WITH DI EXTRACTION WATER AFTER TREATMENT WITH TGPA Radionuclide/ TS-7TS-8 TS-9 TS-10 Isotope/Item CONTROL 3% TGPA 5% TGPA 10% TGPA Ra-226  940 +/− 278 <MDA <MDA <MDA U-235   55 +/− 40 <MDA <MDA <MDA U-238*1,807 +/− 57 30.1 +/− 1.0  8.8 +/− 0.1 7.3 +/− 0.1 Th-234   103 +/− 89<MDA <MDA <MDA Tc-99   207 +/− 15 55.6 +/− 7.8 23.2 +/− 6.5 — U 1,277+/− 40  4.4 +/− 0.1  5.2 +/− 0.1 5.9 +/− 0.1 U, total (ug/l) 2,640 9.110.6 12.1 NOTE: All units in pCi/l, unless indicated *U-238concentrations were calculated. <MDA = less than the calculated MinimumDetectable Activity (MDA) for the counted sample

Examples 13 and 14 demonstrate additional uses for the presentinvention. Sample material and RGW for Examples 13 and 14 were obtainedfrom the Midwestern United States site. To establish baseline untreatedcharacterization data, RGW and soil+RGW samples were tested forradionuclides and other radioactive substances using SPLP and RGW/TCLPextraction methods, prior to adding TGPA to the sample material. Thefollowing tests were performed:

1) RGW was tested for total radionuclides and other radioactivesubstances (US-7);

2) RGW was mixed into the sample material at 30% (wt.). Radionuclidesand other radioactive substances were examined in the amended samplematerial's SPLP extract (US-8); and

(3) DI water was mixed into the sample material at 30% (wt.).Radionuclides and other radioactive substances were examined in theamended sample material's modified TCLP extract where RGW was utilizedas the substitute TCLP extraction fluid (US-9).

Table XIX presents the baseline data. Previous SPLP extraction testresults from the same sample material amended only with DI water (US-5)are presented for comparison.

TABLE XIX BASELINE RADIONUCLIDE LEACHABILITY FOR UNTREATED SAMPLEMATERIAL USING RADIOACTIVE GROUNDWATER (RGW) AS A DISPERSING AGENT ANDEXTRACTION FLUID US-8 US-9 US-5 US-7 30% RGW 30% DI H₂O 30% DI WaterRadionuclide/ RGW SPLP RGW as SPLP Isotope/Item Totals Extract TCLPFluid Extract Bi-211    234 +/− 18 <MDA <MDA <MDA Ra-224 <MDA <MDA   254+/− 131 <MDA Pb-212 <MDA <MDA  27.8 +/− 11.7 <MDA Ra-226     6 +/− 7<MDA <MDA <MDA U-235  9,251 +/− 1,341 261 +/− 49  8,353 +/− 115  9,190+/− 43 Th-234  35,940 +/− 5,027 560 +/− 113 26,220 +/− 462  3,355 +/− 90U, total (mg/l)  97,431 7,813 66,471 16,375 U-238 (ug/l)  45,793 3,69631,441 11,210 Tc-99 126,790 580 +/− 30 63,241 +/− 589   152 +/− 10 pH(S.U.) 7.5 TSS (mg/l)  1,320 TDS (mg/l)  4,400 Hardness [CaCO₃ (mg/l)] 1,734 * U-238 concentrations were calculated. All units expressed aspCi/l, unless indicated <MDA = less than Minimum Detectable Activity forthe counted sample.

EXAMPLE 13

In Example 13, the effects of extracting TGPA treated radioactive samplematerial containing RGW with USEPA's simulated acid rain leaching method(SPLP) are presented. In this example, RGW was used as a dispersionagent in place of deionized water. Contaminated sample material(characterized in Table XIX) was mixed with RGW at 30% (wt.). Three (3)equivalent aliquots of the sample material mixed with RGW were placed inseparate beakers. In the first beaker, TGPA was added at a dose of 2%(wt.) and mixed (TS-11). In the second beaker, TGPA was added at a doseof 5% (wt.) and mixed (TS-12). In the third beaker, TGPA was added at adose of 10% (wt.) and mixed (TS-13). The amount of TGPA added wascalculated from the base mass of the untreated sample material exclusiveof the RGW mass added.

Table XX presents the data from the analysis of SPLP extract for each ofthe treated samples (TS-11, 12, and 13). The untreated characterizationdata from samples (US-7, and US-8) are presented in Table XIX forcomparison. The SPLP extraction (SW-846, Method 1312) is USEPA'sprocedure for simulating soil exposure to acid rain. The SPLP methodcalls for the extraction of 100 g of material with 2000 ml of simulatedacid rain fluid.

TABLE XX TGPA SOIL TREATMENT RESULTS: RADIONUCLIDES IN SPLP EXTRACT OFSAMPLE MATERIAL MIXED WITH 30% (WT.) RADIOACTIVE GROUNDWATERRadionuclide/ TS-11 TS-12 TS-13 Isotope/ Treated Treated Treated Item 2%TGPA 5% TGPA 10% TGPA Bi-211 <MDA <MDA <MDA Ra-226 <MDA <MDA <MDA U-235<MDA <MDA <MDA Th-234 <MDA <MDA <MDA U, total, (mg/l) 30 19 38 U-238(ug/l)* 14  9 18 Tc-99 292 ± 21 322 ± 23 280 ± 21 RGW (characterized inUS-7) was added to TS-11, TS-12, and TS-13 at a dose of 30% (wt.) priorto TGPA addition. All units expressed as pCi/i, unless indicated. <MDA =less than Minimum Detectable Activity for the counted sample *U-238concentrations were calculated.

EXAMPLE 14

In Example 14, sample materials containing radionuclides and otherradioactive substances was treated with varying doses of TGPA and DIwater was utilized as a dispersing agent. These treated samples werethen extracted using the modified TCLP method (RGW/TCLP) where RGW wassubstituted for the specified extraction fluid (TCLP Fluid No. 2). Thesample material was mixed with DI water and three (3) equivalentaliquots of the material were placed in separate beakers. In the firstbeaker, TGPA was added at a dose of 2% (wt.) and mixed (TS-14). In thesecond beaker, TGPA was added at a dose of 5% (wt.) and mixed (TS-15).In the third beaker, TGPA was added at a dose of 10% (wt.) and mixed(TS-16). The percent weight of TGPA added was calculated from theinitial base mass of the untreated sample material exclusive of the RGWmass added.

Each of the treated samples were then extracted using the RGW/TCLPmethod with RGW fluid added at the method specified volume and ratio(100 g soil: 2000 ml fluid).

Table XXI presents the data from the analysis of the modified RGW/TCLPextract for each of the treated samples (TS-14, 15, and 16). Theuntreated characterization data from RGW (US-7) and untreated soilextract by RGW/TCLP (US-9) are presented in Table XIX for comparison.

TABLE XXI TGPA TREATMENT RESULTS: RADIONUCLIDES IN MODIFIED RGW/TCLPEXTRACT OF SAMPLE MATERIAL MIXED WITh 30% (WT.) DI WATER TS-14 TS-15TS-16 Radionuclide/ 2% TGPA 5% TGPA 10% TGPA Isotope RGW/TCLP RGW/TCLPRGW/TCLP Bi-211 <MDA <MDA <MDA Ra-226 <MDA <MDA <MDA U-235  2,513 ± 461 1,919 ± 267 <MDA Th-234 <MDA  5,656 ± 790   200 ± 170 U, total (mg/l)18,191 11,880 18 U-238 (ug/l)*  8,604  5,619  9 Tc-99 45,738 ± 22260,398 ± 255 35,176 ± 195 2000 ml of RGW (characterized in US-7) wasadded as the TCLP extraction fluid to 100 g of the treated samplematrix. An units expressed as pCi/i, unless indicated. <MDA = less thanMinimum Detectable Activity for the counted sample *U-238 concentrationswere calculated.

Examples 13 and 14 show that the present invention can use radioactivegroundwater as a dispersing agent and that materials treated by thepresent invention can be used to treat RGW. These examples alsodemonstrate that acid rain will not affect treated material.

EXAMPLE 15

Example 15 examines the leachability of constituents from a hostmaterial based on a calculation of the distribution coefficient (K_(d))for a given analyte (e.g., a specific constituent measured by theanalyses). The distribution coefficient is expressed in ml/g andcalculated as the quotient of the activity of nuclide sorbed per unitmass of host material (expressed in pCi/g), and the activity of thenuclide in extract solution per unit volume of extract (expressed inpCi/ml). K_(d) is an equilibrium value often calculated to determine thesorption affinity of waste analytes (e.g., nuclides) by host matrix(e.g., contaminated material) in aqueous or other fluid suspensions. Inthis example, the distribution coefficients are calculated for theuntreated (Table XXII) and TGPA treated material (Table XXIII). The samecalculations can be made for similar extractions using other extractionfluids such as, deionized water, SPLP or RGW.

TABLE XXII CALCULATED DISTRIBUTION COEFFICIENT (KD) OF UNTREATED SAMPLEMATERIAL MODIFIED USING SW-846, METHOD 1311 EXTRACTION METHOD US-10 US-1US-1 Modified Total TCLP TCLP Distribution Activity Fluid 2 Fluid 2Coefficient (K_(d)) ANALYTE (pCi/g) (pCi/l) (pCi/ml) (ml/g) Pb-210   179  173 0.173 1,034.7 Bi-211 4,212 3,360 3.360 1,253.6 Bi-214 1,321   9100.910 1,373.6 Fr-223 3,919 3,768 3.768 1,040.1 Ra-223 1,574 1,514 1.5141,039.6 Ra-224 2,463 1,772 1.772 1,390.0 Ra-226 1,800 1,294 1.2941,391.0 Ac-227   188   243 0.243   773.7 Th-227   960   921 0.9211,042.3 Th-228 17,110  16,490  16.490  1,037.6 Pa-231 1,857 1,764 1.7641,052.7 U-235   326   313 0.313 1,041.5 Th-234 NT   19 0.019 —

TABLE XXIII CALCULATED DISTRIBUTION COEFFICIENT (KD) OF TGPA TREATEDSAMPLE MATERIAL MODIFIED USING SW-846, METHOD 1311 EXTRACTION METHODUS-10 TS-1 TS-1 Untreated 5% TGPA 5% TGPA Modified Material TCLP TCLPDistribution Total Activity Extract Extract Coefficient (K_(d)) ANALYTE(pCi/g) (pCi/l) (pCi/ml) (ml/g) Pb-210   179 <82 <0.082  >2,183 Bi-2114,212 <21 <0.021 >200,571  Bi-214 1,321 <21 <0.021 >62,905 Pb-214 1,250<20 <0.020 >62,500 Fr-223 3,919 <226  <0.226 >17,341 Ra-223 1,574 <37<0.037 >42,541 Ra-224 2,463 <50 <0.050 >49,260 Ra-226 1,800 <190  <0.190 >9,474 Ac-227   188 <44 <0.044  >4,273 Th-227   960 <56 <0.056 >17,143Th-228 17,110  <588  <0.588 >29,099 Pa-231 1,857 <272  <0.272  >6,827U-235   326 <104  <0.104  >3,135 Th-234 NT <12 <0.012 NA

Tables XXII and XXIII show an increase of the sorption affinity of theradionuclides by the host material as a result of treatment with TGPA.Further, the calculations in Tables XXII and XXIII utilize the MDAvalues for the equation denominator. The MDA is based on numerousfactors, including count times, background, detector efficiency,recovery, decay, and other variables. Therefore, the K_(d) values forradionuclides in materials treated with TGPA are actually higher thanwhat can be empirically determined when the nuclide presence in extractis <MDA.

Although the present invention has been described in connection withpreferred embodiments, it will be appreciated by those skilled in theart that additions, modifications, substitutions and deletions notspecifically described may be made without departing from the spirit andscope of the invention defined in the appended claims.

What is claimed is:
 1. A process for treating a material that contains aleachable radioactive substances, said process comprising the steps of:contacting said material with technical grade phosphoric acid to producea mixture; and curing said mixture for a period of time; wherein theconcentration of leachable radioactive substances in said material sotreated is decreased and non-leachable solid materials are formed.
 2. Aprocess for treating a material that contains leachable radioactivesubstances, said process comprising the steps of: contacting saidmaterial with phosphoric acid and a sulfate, hydroxide, chloride,flouride, halide, halite, silicate, alum, Portland cement, calcium oxideor mixture thereof to produce a mixture; and curing said mixture for aperiod of time; wherein the concentration of leachable radioactivesubstances in said material so treated is decreased and non-leachablesolid materials are formed.
 3. A process for treating a material thatcontains leachable radioactive substances, said process comprising thesteps of: contacting said material with phosphoric acid to produce amixture; and curing said mixture for a period of time; wherein theconcentration of leachable radioactive substances in said material sotreated is decreased and non-leachable solid materials are formed andwherein said material treated is a solid.
 4. The process according toclaim 1, wherein said material treated is a liquid.
 5. A process fortreating a material that contains leachable radioactive substances, saidprocess comprising the steps of: contacting said material withphosphoric acid and a mono-, di-, or tribasic phosphate to produce amixture; and curing said mixture for a period of time; wherein theconcentration of leachable radioactive substances in said material sotreated is decreased and non-leachable solid materials are formed. 6.The process according to claim 2, wherein said sulfate is calciumsulfate, gypsum, sulfuric acid or mixtures thereof.
 7. The processaccording to claim 2, wherein said sulfate is a liquid.
 8. The processaccording to claim 1, wherein said technical grade phosphoric acid is upto 30 percent of the weight of the material treated.
 9. A process fortreating a material that contains leachable radioactive substances, saidprocess comprising the steps of: contacting said material withphosphoric acid to produce a mixture; and curing said mixture for aperiod of time; wherein the concentration of leachable radioactivesubstances in said material so treated is decreased and non-leachablesolid materials are formed and wherein said material treated is selectedfrom the group consisting of soils, debris, sludges, slag, sand, silts,sediments, industrial waste and solid waste materials.
 10. A process fortreating a material that contains a leachable radioactive substance,said process comprising the steps of: contacting said substance withtechnical grade phosphoric acid to produce a mixture; and curing saidmixture for a period of time; wherein the concentration of leachableradioactive substances in said material so treated is decreased andnon-leachable solid materials are formed.
 11. The process according toclaim 10, wherein said material treated is selected from the groupconsisting of soils, debris, sludges, slag, sand, silts, sediments,industrial waste and solid waste materials.
 12. The process according toclaim 10, further comprising contacting said mixture with a sulfate,hydroxide, chloride, fluoride, halide, halite, silicate, alum, Portlandcement, calcium oxide or mixture thereof prior to curing.
 13. Theprocess according to claim 10, further comprising contacting saidmaterial with a dispersion agent.
 14. The process according to claim 10,further comprising contacting said material with water containingradioactive substances.
 15. The process according to claim 10, whereinsaid phosphoric acid is up to 30 percent of the weight of the materialtreated.
 16. A process for treating a material that contains a leachableradioactive substance, said process comprising: contacting saidsubstance with technical grade phosphoric acid; wherein theconcentration of leachable radioactive substances in said material sotreated is decreased by more than 90%, non-leachable solid materials areformed and no secondary waste streams are generated.
 17. The processaccording to claim 16, further comprising contacting said material witha sulfate, hydroxide, chloride, fluoride, halide, halite, silicate,alum, Portland cement, calcium oxide or mixture thereof.
 18. The processaccording to claim 16, further comprising contacting said material withwater containing radioactive substances.
 19. The process according toclaim 16, wherein said phosphoric acid is up to 30 percent of the weightof the material treated.